Analysis of resonance effect for a railway track on a layered ground

Abstract

When a train runs on soft ground it can approach or even exceed the speed of surface waves in the ground. Under such conditions the amplitudes of the track response increase considerably.Moreover, a resonance-like phenomenon can occur in which a clear oscillation trail can be observed behind the moving axle loads. An investigation is presented of this resonance frequency and the critical speed effect for a track on a layered half-space subject to a moving load. Three different methods are used to investigate this resonance frequency: (i) the spectrum of the response to a moving load, (ii) analysis of the dispersion curves of the ground, and (iii) frequency analysis of the response to a stationary load. A parameter study is presented of a layered half-space ground with different P-wave speeds, S-wave speeds, and depth of the upper layer. The critical speeds are found in each case; in such a layered ground, the critical speed is greater than the Rayleigh wave speed of the soft upper layer due to the influence of the underlying half-space. The oscillating frequencies are shown to vary with the speed of the moving load, tending to reduce when the load speed increases. The P-wave speeds of both the upper layer and the underlying half-space are found to have negligible influence on the critical velocity and on the oscillating frequency; the S-wave speed of the half-space has only a small influence. Larger differences are found when the depth of the layer is varied. Finally, a formula for calculating this resonance frequency is proposed.

Modelling, simulation and evaluation of ground vibration caused by rail vehicles

“…For soft soil, a strong coupling exists between the soil and the track, and a resonance-like phenomenon occurs in high-speed cases [162]. Non-linearity should then not be neglected in prediction models.…”

Railway critical speed assessment: A simple experimental-analytical approach

“…In contrast, the simplified approach is based on the analysis of the dispersion characteristics of the waves propagating along the track-ground system. This approach is efficient from a computational point of view because it doesn't require the computation of the dynamic track response due to moving loads [4,13,14]. More recently Norén-Cosgrif et al [15] proposed a method for critical speed prediction based on experimental data.…”